Jin Bo, Yuan Caixia, Guo Jin-Chang, Wu Yan-Bo
Key Laboratory of Materials for Energy Conversion and Storage of Shanxi Province, Institute of Molecular Science, Shanxi University, 92 Wucheng Road, Taiyuan, Shanxi, 030006, People's Republic of China.
Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Molecular Science, Shanxi University, 92 Wucheng Road, Taiyuan, Shanxi, 030006, People's Republic of China.
Nanoscale. 2024 Feb 29;16(9):4778-4786. doi: 10.1039/d3nr05695c.
It is highly challenging to control (stop and resume as needed) molecular rotors because their intramolecular rotations are electronically enabled by delocalized σ bonding, and the desired control needs to be able to destroy and restore such σ bonding, which usually means difficult chemical manipulation (substitution or doping atom). In this work, we report CBeH, a molecular rotor that can be controlled independently of chemical manipulation. This molecule exhibited the uninterrupted free rotation of Be and H atoms around the central carbon in first-principles molecular dynamics simulations at high temperatures (600 and 1000 K), but the rotation cannot be witnessed in the simulation at room temperature (298 K). Specifically, when a C-H bond in the CBeH molecule adopts the equatorial configuration at 298 K, it destroys the central delocalized σ bonding and blocks the intramolecular rotation (the rotor is turned "OFF"); when it can adopt the axial configuration at 600 and 1000 K, the central delocalized σ bonding can be restored and the intramolecular rotation can be resumed (the rotor is turned "ON"). Neutral CBeH is thermodynamically favorable and electronically stable, as reflected by a wide HOMO-LUMO gap of 7.99 eV, a high vertical detachment energy of 9.79 eV, and a positive electron affinity of 0.24 eV, so it may be stable enough for the synthesis, not only in the gas phase, but also in the condensed phase.
控制（按需停止和恢复）分子转子极具挑战性，因为它们的分子内旋转是由离域σ键实现电子驱动的，而所需的控制需要能够破坏并恢复这种σ键，这通常意味着困难的化学操作（取代或掺杂原子）。在这项工作中，我们报道了CBeH，一种无需化学操作就能被控制的分子转子。在高温（600和1000 K）下的第一性原理分子动力学模拟中，该分子表现出Be和H原子围绕中心碳的不间断自由旋转，但在室温（298 K）模拟中无法观察到这种旋转。具体而言，当CBeH分子中的C-H键在298 K时呈赤道构型时，它会破坏中心离域σ键并阻止分子内旋转（转子“关闭”）；当它在600和1000 K时能呈轴向构型时，中心离域σ键可以恢复，分子内旋转可以恢复（转子“开启”）。中性CBeH在热力学上是有利的且电子稳定，这体现在其7.99 eV的宽HOMO-LUMO能隙、9.79 eV的高垂直脱附能和0.24 eV的正电子亲和势上，所以它可能足够稳定以进行合成，不仅在气相中，在凝聚相中也可以。
